Customers of electric utility companies often desire a back-up electrical power supply during a power outage. Typically, such a back-up is provided by an alternate power supply such as a fuel-fired engine-driven power generator, an inverter, solar cells or fuel cells, for example. A common method used is the installation of a power generator which is interfaced with an automatic or manual transfer switch that is capable of simultaneously disconnecting the electric utility (mains) power supply and connecting the alternate power supply to the facility loads.
Manual transfer switches usually require an operator to first start the power generator, and then actuate a handle in order to initiate the power transfer. Automatic transfer switches enable unattended operation where monitoring circuits automatically detect power disturbances, initiate automatic starting of the generator system, and proceed to transfer power from one supply to the other using an electrically operated mechanism. The process is reversed when power is restored.
Among the problems typically confronting a user of electricity wishing to install a back-up power supply is the installation complexity of a traditional transfer switch. Installation of either manual or automatic transfer switches requires extensive modification of the user's electrical wiring system in the facility. This is an expensive process as it must be performed by electrical professionals and it is a time consuming process due to safety concerns and the requirement for compliance with various safety standards. In many cases, this also involves separating the critical loads that the user wishes to back-up by connecting them to a sub-panel, which in turn is connected to the transfer switch. In this scenario, only those loads connected to the sub-panel are capable of drawing power from the generator system, which is inconvenient for many users.
Accordingly, it is desirable to provide a transfer switch where power is switched ahead of the facility's service entrance means to permit the engagement of any load within the facility. This allows the purchaser to avoid the installation of an electrical sub-panel and increases the convenience to the user. Still further, it is desirable to provide a rapid and inexpensive means to install a transfer switch for engagement with the electrical system.